Flash Techniques #4: How to Slow Sync with a Built-In Flash

When photographing portraits against the backdrop of a brilliant sunset, not using a flash will result in insufficient light, and an overall darker image. However, if you use the built-in flash, you run the risk of the background becoming pitch black, without the fiery sunset in the background. In this article I will introduce an applied technique using the built-in flash that is handy for such instances. (Reported by: Teppei Kohno)

Set the exposure in accordance with the background, and illuminate the person with the flash light

*Shooting Procedure
A: Set the exposure so that you can beautifully capture the sunset.
B: Arrange the person and background well for the composition, and then focus on the person.
C: Take shots with the built-in flash on.
D: Check the resulting photos, and if necessary, adjust the flash exposure compensation.

When you take portraits against the background of a beautiful sunset, since there is only a small amount of light after the sun has set, the sunset that you capture will be darker than expected. For shooting scenes like this, first consider matching the exposure with the sunset. Set an exposure for which the colours of the sky are captured beautifully with a slow shutter speed, and use the built-in flash to compensate the brightness of the person in the foreground. This technique is referred to as Slow Sync.

I took a test shot using Aperture-Priority AE, and checked the f-number and shutter speed at which the background was properly captured. I then switched the shooting mode to Manual, set the values obtained during the test shoot, and fixed the exposure. Adjust the flash exposure compensation for the built-in flash until the brightness is just right for the subject of the shoot. If blurring occurs due to the shutter speed being too slow, I recommend using a tripod or placing the camera on a stand.

Negative example: 1/60 sec

Good example: 1 sec

Left: EOS 760D/ EF-S18-55mm f/3.5-5.6 IS STM/ FL: 27mm (43mm equivalent)/ Program AE (f/4, 1/60 sec)/ ISO 200/ WB: Auto
I set the shutter speed to 1/60 second, and used the built-in flash. The shutter speed was too fast, so only the person was captured, while the sunset was lost.

Right: EOS 760D/ EF-S18-55mm f/3.5-5.6 IS STM/ FL: 27mm (43mm equivalent)/ Manual exposure (f/4, 1 sec)/ ISO 200/ WB: Auto
I set the shutter speed to 1 second, and used the built-in flash. I was able to capture both the person and sunset beautifully.

Point-to-note!

Have the subject move during the shoot to evoke a sense of motion

When using a slow shutter speed, any movement while the shutter is open will be blurred in the photo. You can take advantage of this by having the person deliberately move to evoke a sense of motion in the photo. I asked my subject to keep her face still while having her sway her body from side to side. The movement of her hair and clothing is depicted in the resulting motion blur.

I set the shutter speed to 1 second, and used the built-in flash. The lady swayed her body from side to side while the shutter was released. In this way, I was able to take a photo that evoked a sense of motion while making the most of the colours of the sunset sky.

Use an externally-mounted Speedlite when you want more light

When the shooting distance to the person becomes further, the amount of light provided by the build-in flash might be insufficient. Also, when you try to be creative with the composition, such as by placing the person in the corner of the frame, there may be times when you want to adjust the angle of the light emitted from the flash. For these cases, I recommend using an externally-mounted Speedlite. The SPEEDLITE 430EX III-RT is easy to use thanks to its compact size, has plenty of light with its guide number of 43 (the built-in flash of the EOS 760D is GN12), and the angle of the flash head can be changed.

Born in Tokyo in 1976, Kohno graduated with a Social Work degree from the Department of Sociology of Meiji Gakuin University, and apprenticed with photographer Masato Terauchi. He contributed to the first issue of photography magazine PHaT PHOTO and became an independent photographer after that, in 2003. The author of many books, Kohno not only shoots all sorts of commercial photographs, but also writes prolifically for camera and other magazines.

For dark indoor scenes, the face of the subject may be unnaturally illuminated when you use the built-in flash. In this article, we teach you how to fix this by varying the amount of light from the built-in flash. You can adjust the settings to get the level of brightness you want. (Reported by: Teppei Kohno) ...

Darkening the background and brightening your subject allows you to take dramatic portraits that make it look as if the person is bathed in a spotlight, making them the centre of attention. By using this technique outdoors, it is possible to take impressive and sometimes surreal-looking images. This is a technique called daylight sync, and in this article, we show you how you can use flash exposure compensation to adjust the light of your built-in flash for best results. (Reported by: Teppei Kohno) ...

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